BioCycle April 2010, Vol. 51, No. 4, p. 60
I gave a talk on the benefits of compost use at a U.S. EPA meeting last year and said that if there were a beauty product with just half of the quantifiable benefits of compost, its sales would be astronomical. To understand that comment, we need to start by talking about beauty products. I realize that many of you are “men” who don’t spend nearly as much time talking about beauty products as the stereotypical woman does. We don’t have to talk about this publicly, but I happen to live with a man, and not a metrosexual type of man, who uses more beauty products than I do. You may not want to fess up to this in public but I am sure that everyone reading this column has some awareness of the beauty products industry.
With beauty products, there are a wide range of choices and prices. You don’t randomly go and pick some product off the shelf. You target your purchase for your particular need. And you also don’t generally over apply. You may purchase based on familiarity with a name brand or by a friend’s recommendation. You may also purchase because of a targeted marketing campaign. And you would certainly never use eye cream on your feet or hair dye on your face.
What I’m getting at is beauty products are not one big generic thing that just comes in different jars with different price tags. They are carefully honed products, developed very specifically for a target audience and are generally used for specific purposes. Sound familiar?
The claims on the beauty products are things like “natural looking,” “slows down aging,” “smooth silky skin.” Nowhere on these products do you find things like a “50% increase in skin resiliency.”
If you look at the literature on organic soil amendments, on the other hand, you do start to see numbers, real numbers, some of them as high as 50 percent for things like increases in soil organic carbon, water holding capacity, water infiltration rate and plant yield. And if you read in greater detail, you will see that these increases are not across the board for all soils, climates and crops.
SOIL AND CARBON EXAMPLE
Carbon storage is a case in point. We are writing up a study where we sampled a range of sites – farm fields and replicated field studies that have a history of compost or biosolids use. Although adding compost or biosolids increased soil carbon storage for every site tested, there was a wide range in values for response to organic additions. In the nice soils, maintained without tillage in turf grass, this increase was the smallest. (Continuous grass is a great way to build soil carbon; our best agricultural soils are in the Midwest.) For one of the grass plots, we found just 0.01 tons of soil carbon per ton of compost added. And that was at a very high loading rate.
By comparison, if you look at the carbon response for organics added to a poor soil, that number goes up to 0.36 for biosolids added to dryland wheat, 0.45 for compost added to a highly disturbed highway right of way, and 0.53 for compost used on an irrigated pear orchard in the dry part of Washington State. In other words, the benefits associated with use of this beauty treatment are wasted on the young and beautiful. It is us old crows who really need the stuff. If you really want the full bang for your buck, organic amendments will give the best response to disturbed or low organic matter soils.
Here’s another surprise from this sampling: It turns out there are much bigger increases in soil carbon when the compost is incorporated into the soil rather than just left on top. At one site, for example, compost was either surface applied or incorporated. The plots were planted with different ornamental species including dogwoods. Eight years into the study, the soil in the control treatment had one percent carbon. The soil where compost had been spread on the surface had about 1.5 percent carbon and the soil where the compost had been tilled in had close to 2 percent carbon.
A more dramatic version of this was seen at another site where compost was applied to the disturbed soil on a highway border. After two years, carbon in the soil where compost or biosolids had been surface applied was the same as the control (about 0.3-0.4%). When that material was tilled in, soil carbon content jumped to between 4.5 and 5.5 percent.
So not only does it matter where you use these wonderful beauty products for the soil, it matters how you use them. And you show me one bag or truckload of compost that gives this level of detail on instructions for use.
As with all beauty products, there can be some nasty side effects. (I bet more than one of you knows that if you use Retin-A you don’t go bake in the sun.) The same holds true if you make or use compost improperly. For example, one issue for organics is the potential for N2O (nitrous oxide) emissions during composting.
In one study, high rates of N2O were reduced to below detection when the manure feedstocks were mixed with more straw to increase the C:N ratio and bring the moisture content of the pile down. I was asked: “Is it because of the C:N ratio or the moisture content.” All I could say was, good question! If we had as many studies of composting and N2O emissions as there are of skin creams with Retin-A, I could answer that question.
The point of this column is that we are starting to recognize that the benefits associated with organics use will depend on where and how you use them. This is an understanding that is just beginning to be developed using a greenhouse gas lens. This statement also applies to other components of organics use in soils. For example, while there is more literature out there on how to maximize benefits associated with compost use for things like increasing water holding capacity (benefits are much greater in sandy soils), there is not yet a clear quantifiable formula for how to optimize use. This is likely because organic residuals, water and soils have traditionally been looked at as plentiful resources. None of these materials are plentiful resources. But, if we learn to use them properly, we eek out the most value for what we do have.
Sometimes I get frustrated that the resources and attention given to develop a new wrinkle resistant face cream are so much greater than those allotted to products like compost that let us eat. But everyone looks in the mirror every day and very few of us put our hands in the soil every day. As an industry, it is essential for us to spread the message that our treated organic waste streams have the power to restore and replenish our limited water and soil resources (sort of like how beauty products restore our skin). We need to let people know that the fountain of youth (or at least sustainability) is waiting in their trash and their toilet.
Sally Brown, Research Associate Professor at the University of Washington (firstname.lastname@example.org), authors this monthly column on the connections of composting, organics recycling and renewable energy to climate change.